How should diabetes medications be managed while fasting? Fasting for morning labs usually doesn't require adjustments. But other fasts vary. For example, patients may fast from dawn to dusk during Ramadan or from sundown to sundown during Yom Kippur or 18 hours/day with some intermittent fasting diets. Help individualize a plan based on medications, and fast duration...
Medications that rarely cause hypoglycemia include metformin, pioglitazone, gliptins (Januvia, etc) and GLP-1 agonists (Victoza, etc). These can generally be continued for intermittent or religious fasts, but may need to be held before procedures. Labelling says to hold most SGLT2 inhibitors (Jardiance, etc) before surgery due to risk of ketoacidosis. But some experts may also hold them before procedures or religious fasts or if dehydration may occur. Consider this a downside of using SGLT2 inhibitors in patients who plan to do religious fasting or an intermittent fasting diet.
Insulin or sulfonylureas are bigger culprits for hypoglycemia. In general, advise holding mealtime insulin or sulfonylureas once the patient stops eating. But suggest holding sulfonylureas 24 to 36 hours before a longer fast (24 hours, etc). For basal insulin, think of giving about half the usual dose if the patient's well controlled or at higher risk of hypoglycemia (elderly, kidney impairment, etc). Otherwise, consider reducing the dose by about one-third. Suggest reducing doses of NPH or a long-acting analog (Lantus, Levemir, etc) at the START of the fast. But suggest reducing Tresiba the day BEFORE the fast.. since it lasts almost 2 days.
Recommend frequent blood glucose monitoring while fasting in patients on insulin or a sulfonylurea. Advise other patients to check if they have symptoms of hypoglycemia (feeling shaky, dizzy, sweaty, etc). Suggest breaking the fast for glucose below 70 mg/dL (3.9 mmol/L) or if patients have symptoms with glucose below 80 mg/dL (4.4 mmol/L).
REFERENCES
Grajower MM. 24-Hour Fasting with Diabetes: guide to physicians advising patients on medication adjustments prior to religious observances (or outpatient surgical procedures). Diabetes Metab Res Rev. 2011 Jul;27(5):413-8. Available at: https://pubmed.ncbi.nlm.nih.gov/21309050
Ibrahim M, Davies MJ, Ahmad E, Annabi FA, Eckel RH, Ba-Essa EM, El Sayed NA, Hess Fischl A, Houeiss P, Iraqi H, Khochtali I, Khunti K, Masood SN, Mimouni-Zerguini S, Shera S, Tuomilehto J, Umpierrez GE. Recommendations for management of diabetes during Ramadan: update 2020, applying the principles of the ADA/EASD consensus. BMJ Open Diabetes Res Care. 2020 May;8(1):e001248. Available at: https://pubmed.ncbi.nlm.nih.gov/32366501
Diabetes Canada, Ramadan and Diabetes: http://guidelines.diabetes.ca/health-care-provider-tools/ramadan-and-diabetes